Some tips for spray painting on plastic surfaces include cleaning the plastic thoroughly, abrading the plastic and applying primer before painting. Also, spray paint from an appropriate distance, apply the paint evenly, and paint on a test surface before doing the actual job.
To clean the plastic material, wipe it using a clean cloth to remove dust, sticky residue and debris from the surface. If required, apply a water-based degreasing agent over the surface, rinse off the agent, and dry the surface using towels.
Abrade the material to improve adhesion of paint. To do this, use a palm sander with 220-grit sandpaper. After sanding, the surface be slightly gritty.
Determine if the spray paint requires a coat of primer. If so, cover areas you do not wish to spray using a drop cloth or painter's tape, and spray acrylic-based primer sideways in a sweeping motion. Allow the primer to dry for at least three hours.
When using the spray paint, maintain a distance of 4 to 8 inches between the plastic surface and the spray can. Spray using a sweeping, sideways motion to apply the paint evenly. Do not stop until you complete a paint band from one end to the other, and apply the paint slightly beyond the surface's edge before releasing the spray can's trigger.
Allow the paint around three hours to dry. After drying, if the painted surface does not appear smooth, sand the area, and apply the paint again uniformly and from a closer distance. Preferably, spray paint on a test piece of plastic to check the results prior to beginning the job.